There has been an alarming increase in toxic cyanobacteria during the past 2 decades, with numerous poisonings reported from Australia to the United States. The increased toxic risks led the U.S. Environmental Protection Agency (EPA) to include cyanotoxins on the 1998 Contaminant Candidate List. However, most cyanobacterial blooms are not toxic. Further, bloom toxicity will change over time. Therefore, cyanobacterial identification is not enough; toxin presence must be confirmed. There are many biological/toxicological methods available to detect these toxins. The main drawback to these biological techniques is that they are time-consuming, laboratory-based, and require significant technical expertise. However, with a dynamic system like cyanobacterial blooms, detection and identification of toxins should be conducted as quickly as possible, preferably in the field.
In this research project, EIC Laboratories, Inc., will develop a field-portable automated sensor based on Surface-Enhanced Raman Spectroscopy (SERS) that can be used by nonspecialists. The entire system will weigh approximately 10 lbs and will detect different toxins through a simple dipstick arrangement. SERS spectroscopy, which directly measures chemical bonding, theoretically would allow direct determination of all analytes; however, practical identification of the desired toxins in the presence of nontoxic bacteria and other chemical constituents in the water supply could become unwieldy. There are methods by which SERS substrates can be specific for certain analytes using chemical modifications. These modifications can alter the surface chemistry to attract chemicals with a certain electronegativity, pH, or chemical reactivity. In this project, EIC Laboratories, Inc., will use the latter and develop SERS substrates highly specific for the toxins of interest. For example, SERS substrates modified with saxiphilin for detection of the saxitoxin family of cyanotoxins will be developed. The Phase I project will develop SERS sensors that can detect the EPA-defined high-priority toxins anatoxin-a, saxitoxin, and cylindrospermopsin down to < 1 ppb in the presence of anticipated interferences.
The Phase II project will expand the SERS sensor capabilities to detect microcystin, anatoxin-as, nodularin, domoic acid, and other EPA-defined cyanotoxins of interest. The Phase II project also will develop an easy-to-use, automated toxin-sensing system that will weigh approximately 10 lbs and be completely field portable. The technician will dip the sensor into the water supply and then withdraw the sensor. The automated system then will analyze the results and return toxin concentrations, if detected. The final instrument will have a target sensitivity of < 1 ppb and complete selectivity for each cyanotoxin, with no false positives or negatives.